<!DOCTYPE html>
<html>
<head>
<title>WebGL Scissor with context of preserveDrawingBuffer=true</title>
<style type="text/css">
.nomargin {
  margin: 0px auto;
}
</style>

<script>

function run() {
  var canvas = document.getElementById("c");
  gl = initGL(canvas);
  if (!gl) {
    domAutomationController.send("FAILURE");
    return;
  }
  gl.clearColor(1, 0, 0, 1);
  gl.clear(gl.COLOR_BUFFER_BIT);
  window.requestAnimationFrame(scissorAndClear);
}

function initGL(canvas) {
  var gl = null;
  try {
    gl = canvas.getContext(
        "webgl", {preserveDrawingBuffer: true, alpha: false});
  } catch (e) {}
  return gl;
}

function scissorAndClear() {
  gl.scissor(0, 0, 10, 10);
  gl.enable(gl.SCISSOR_TEST);
  gl.clearColor(0, 1, 0, 1);
  gl.clear(gl.COLOR_BUFFER_BIT);

  deferredAck();
}

var swapsBeforeAck = 15;
function deferredAck()
{
  if (swapsBeforeAck == 0) {
    domAutomationController.send("SUCCESS");
  } else {
    --swapsBeforeAck;
    window.requestAnimationFrame(deferredAck);
  }
}

</script>
</head>
<body onload="run()">
<div style="position:absolute; top:0px; left:0px">
<canvas id="c" width="200" height="200" class="nomargin"></canvas>
</div>
</body>
</html>
